Chuck



Sept. 21, 1948. M.H. ARMS ETAL CHUCK Filed April 17. 1945 2 Sheets-Sheet1' [m/z [id/ward W M. H. ARMS ET AL CHUCK Sept. 21, 1948.

2 Sheets-Sheet 2 Filed April 11, 1945 J72 02f MKWZEa XX??? J (0/5[fawzmi alw wa Patented Sept. 21, 1948 Vt., assignors to Bryant ChuckingGrinder Company, Springfield; Vt, a corporation of.

Vermont I Application April 17, 1945, Serial No. 588,784

This invention relates to improved chucks; and more especially tochucksfor grinding machines designed for precision grinding.The-invention further relates to chucks'of thetypeadaptedto be rotatedwhile the work piece held thereby being ground. l

In precision grinding, very high degree of accuracy is often required.For example, an internal cylindrical surface may have to be accuratelyround withina tolerance limit of a few millionthsof an inch. Inattaining accuracy of this order, it is evident that the contact of thegrinding tool with the groundsurface of the work must be very carefullycontrolled.

It is anobiect of this invention to provide a chuck which is constructedto cause uniformity of relative travel between the ground surface andthe tool and thus to avoid irregularities of the depth of the layer ofwork removed by the grind ing tool. To this end the chuck is made torotate, the work being coaxial therewith, and is given a, relativelygreat rotational inertia by an suitable means, such. as a, circularmember of considerable diameter and mass secured thereto or made a partthereof. By rotating the chuck and work above the critical speed; where,due to centrifuga-l force, the center of rotation is about to coincidewith the center of mass of the rotated parts they rotate abouttheir owncenterof gravity whichmay or may not. coincide with-theaxis at rest.

For a more complete disclosure of the invention, reference may be had tothe following de scription thereof, and to the drawings, of which Figure1 is a plan view of a chuck embodying the invention, and a grinding toolassociated therewith, a portion being broken away to show in section.

Figure 2 is a similar view on a larger scale, mostly in section taken onthe line 22 of Figure 1.

Figure 3 is a section on the line 3-3 of Figure 2.

Figure 4 is a face view of the chuck shown in Figure 1.

The drawing illustrates a cylindrical grinding tool l adapted to berotated at high speed to grind the interior cylindrical surface of awork piece W which, for example, may be a thimble. The work is held in arotatable chuck which is massive in comparison with the work, the partsbeing formed so as to give the chuck as a whole a large rotationalinertia.

The chuck comprises a chuck plate or disc l2 the rear face of which isstepped near the periphery so as toprovide an annular shoulder H which 5Claims. (01. 51437.).

can be accuratelymachined to fit against a corresponding similarshoulder IS in the recessed front face of a heavy disc l6 ofconsiderablylarger diameter; to which discthe chuck plate 12 is securedby suitable means such as a seriesof screws I8. The recessing of thefront faceof the disc it allows the work to be supported close tothe'rotational plane of the center of mass of the disc ltand partscarried thereby. The disc l6 has a rearwardly extending relativelythin"annular neck 2%! terminating in a lip 22, the end faceof which, isshaped to be secured against the nose of a hollow work spindle 24 by aseries of screws 25. Within the neck 20 and normally spacedslightlytherefrom is a stop sleeve '21 secured to the spindle nose asby screws28. Contactwith the sleeve limits the flexing of the neck 20 when thechuck is rotated and the disc IE tends to center its rotation about itsmasssaxis. These members revolve about the work axis as flywheel inpromoting accurate uniformity of ro tational velocity and lateralstability of thec-huck. Such uniformity and stability is important ingrinding operations of extremely great accuracy since thetime the toolisin contact with suecessive elements of work surface over which it.

moves is a factor in determining the amount of material removed fromeach such element. Hence, any unevenness of relative movement betweenthe tool and the work surface would result in uneven depth of materialremoved.

The chuck disc [2 is centrally countersunk to receive a ring 30 which issecured thereto by a number of screws 32. This ring has an annularsurface 34 which is accurately ground to be in a plane perpendicular tothe axis of the ring. An end of the work piece rests against the surface34 when the work is set up in the chuck.

The work piece is laterally engaged by three jaws 36 symmetricallyspaced around the axis. These jaws are radially arranged On the face ofthe chuck disc and are slidable in radial grooves in the face of thedisc. Each jaw 35 is secured in adjusted position by a screw 38 whichextends through a longitudinal slot 40 in the jaw and into a threadedhole in the disc. To provide for fine adjustment of the jawslongitudinally, each jaw is provided with a screw 42 which bears againstits outer end and in threaded engagement with a boss M on the face ofthe disc I2 and adjacent to the circumference thereof. The inner ends ofthe jaws 3B bear against the work piece to keep it accurately centered.

The work piece is pressed firm ly against the surface 34 during thegrinding operation. For this purpose a forked lever 46 is rockablymounted on the disc. A screw 48 which is threaded into the disc I2 andprojects therefrom between the legs of the lever 46 provides a fulcrumfor the lever midway between its ends. The lever is engaged betweenwashers 52 and 53 having suitable knife edges 50, the washer 52 beingpressed against the head of the screw 48 by a spring 54 which iscompressed between the face of the disc 12 and the outer end portion ofthe lever 46. The pressure of the spring 54 at the outer end of thelever causes the fingers 56 at the forked end of the lever to bearagainst the work piece or, as shown, against a ring 58 looselysurrounding the tubular portion of the work piece and pressing againstthe flange thereof.

Preferably the work piece has a portion such as the flange 45 accuratelypre-ground to size and the inner ends of the jaws are also preground sothat no adjustment of the jaws is necessary for each work piece which ismerely inserted in position and held by the lever '46. When necessary onaccount of wear, the jaws may be adjusted inwardly a slight amount andthe Work engaging faces reground in place of the proper diameter tocenter the work.

To preserve a dynamic balance in the chuck assembly, a pair of weights60 are mounted on the disc to counterbalance the lever 46 and itsassociated parts.

From the foregoing description of an embodiment of this invention itwill be evident to those skilled in the art that various changes andmodifications might be made without departing from the spirit or scopeof the invention.

We claim:

1. Apparatus of the class described comprising a rotary work spindleshaft, chuck mechanism including means for aocunatefly-centering theWork, and a heavy disk having a relatively thin .neck portion securingsaid disk coaicially to said shaft and supporting said chuck, said diskproviding large rotational inertia to said mechanism and said neckportion providing a connection capable of flexing when said mechanism isrotated above critical speed.

2. A work-holding spindle comprising a shaft, a chuck secured thereto,said chulck including independently adjustable jaws, a spring-pressedlever to engage the work, and counterweights to provide dynamic balance,and an inertia member of larger diameter and mass than said chucksecured coaxialiy'to said shaft;

3. Apparatus of the class described, comprising a rotary work spindleshaft, a disk member having large rotational inertia and having arelatively thin neck portion secured to said spindle and about whichsaid neck portion said member may flex when rotated at and abovecritical speed, and a work-holding chuck carried by said memher.

4. Apparatus of the class described, comprising a rotary work spindleshaft, a disk member having large rotational inertia and having arelatively thin neck portion secured to said spindle and about whichsaid neck portion said member may flex when rotated at and abovecritical speed, a-work-holding chuck carried by said member, and meansfor limiting the flexure permitted to said neck portion. j i 5.Apparatus of the class described, comprising a rotary work spind leshaft, a disk member having large rotational inertia and having arelatively thin neck portion secured to saidv LEON J. BARNARD.

I REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date Number Name 222,901 Heckendorn -4 Dec. 23,1879 1,239,873 Bright Sept. 11, 1917 1,544,521 Sosa June 30, 1925.1,762,810 Brittain et al. June10, 1930 1,766,839 Roberts 1 June 24, 19301,778,675 Kempton et al Oct. 14, 1930 2,327,606 Saltz Aug. .24, 19432,371,089 Weddell Mar. 6,1945

